The invention concerns a device that is capable of forming a temporary connection between two elements and using a pyrotechnic composition to control the displacement of a moving part, in order to separate said elements without requiring the breakage of any part whatsoever.
Such a device could in particular be used in the aeronautical and space industries to rapidly separate two structural elements, while at the same time ensuring the transmission of any large forces as required between these two elements before the separation occurs.
When two elements between which forces are transferred require to be very rapidly and irreversibly separated by remote control, it is common practice to use pyrotechnic separation devices incorporated within the connection zone of the two elements
The pyrotechnic separation devices generally comprise a pyrotechnic expansion tube, that is to say a sealed, deformable metal tube containing a detonating fuse. A flexible material such as rubber is placed between the detonating fuse and the surrounding tube. Prior to firing, the tube has an oblong cross section, for example of an elliptical or flattened circular shape.
When the detonating fuse is ignited, the shock wave that travels at very high speed along the length of the tube deforms it and tends to give it a circular cross section.
In existing pyrotechnic separation devices, the pyrotechnic expansion tube is used to cut one of the two elements along a given cutting line so as to separate the two elements from one another.
In the case where the elements to be separated are metallic, it is known for the pyrotechnic expansion tube to be housed in the base of a U-shaped recess formed in one of these elements. The other element is then connected into the opening of this recess, for example by means of bolts or similar. The ignition of the detonating fuse causes the two side legs of the recessed element to break along lines defined by zones of reduced thickness. Documents FR-A-2 598 796 and EP-A-0 273 061 illustrate devices of this type.
It is also known, as shown by document U.S. Pat. No. 4,137,848, for the pyrotechnic expansion tube to be housed between two facing parts of the metallic elements to be separated, by reducing the thickness of on of said parts. The two elements are connected to one another by bolts or similar, to one side of the tube and in proximity to it. The ignition of the detonating fuse causes the part of reduced thickness to break.
Document U.S. Pat. No. 3,362,290 describes an arrangement very similar to that described in documents FR-A-2 598 796 and EP-A-0 273 061. However, instead of causing the recessed element to break, in this case the ignition of the detonating fuse causes the shearing of the rivets that serve to connect the two elements before their separation. To this end, the rivets are hollow and of small diameter.
Where the elements to be separated are of a sandwich construction, it has been proposed to house the pyrotechnic expansion tube in a part of these structures devoid of a hollow core. Igniting the detonating fuse then has the effect of cutting the parts of the cladding situated opposite said tube. Arrangements of this type are described in documents FR-A-2 779 223 and FR-A-2 779 224.
Document FR-A-2 779 222 describes a similar arrangement, in which the two elements are initially connected to one another by at least one glued connecting piece. When the fuse is ignited, the expansion of the tube causes the connection piece to come loose and the two elements to separate.
In summary, all of the known pyrotechnic separation devices used in conjunction with metallic parts achieve the separation of said parts by causing one of them to break or shearing the components that connect them together. The same generally also applies in the case of devices used with parts made from composite materials.
The only exception to this is the case of the mechanism described document FR-A-2 779 22, in which the cutting of one of the two elements is replaced by the removal of a glued connecting component. This type of device can, however, only be used for connecting elements made from composite materials.
The purpose of the invention is the creation of a pyrotechnic separation device, the original design of which enables it to separate elements of any material, in particular metal, without causing the breakage of any part.
According to the invention, this result is obtained by means of a temporary connection and pyrotechnic separation device, consisting of a pyrotechnic composition installed in the connecting area between two elements to be separated, characterised in that the device comprises, in addition, at least one connecting component normally occupying an assembled position in which said connecting component is simultaneously in contact with each of said elements, and a moving part normally occupying a first position in which it maintains the connecting component in its assembled position, the pyrotechnic composition being positioned in such a way as to displace the moving part, under the effect of the pressure of the gases produced, to a second position in which it frees the connecting component, when said pyrotechnic composition is activated.
In this arrangement, the temporary connection between the two elements is ensured jointly by the connecting components, which are in contact with said elements when in their assembled position, and by the moving part, which maintains the connecting components in their assembled position as long as the pyrotechnic composition has not been activated.
According to a preferred embodiment of the invention, the moving part is able to slide over a first of said elements and the pyrotechnic composition is housed between two shoulders formed on the moving part and the first element respectively. Hence, the connecting element is secured in its assembled position when the moving part is in its first position. The activation of the pyrotechnic composition has the effect of displacing the moving part away from the second element and releasing the moving part.
In this case, where the two elements are cylindrical or oval, the moving part will advantageously comprises a deformable section that encloses the connecting component when the moving part is in its first position. This deformable section will then be fitted with clamping means.
The deformable section of the moving part preferably includes separate annular segments, each of which is connected at its centre to a principal section of the moving part, the clamping means being interposed between the adjacent ends of the segments.
The clamping means can in particular consist of tension devices bearing on flanges attached to the adjacent ends of the segments.
Also according to the preferred embodiment of the invention, each connecting component consists of a U-bracket comprising an inner face with a first projecting part and a second projecting part which are accommodated respectively in a first recessed section formed in the first element and in a second recessed section formed in the second element, when the connecting component is in its assembled position.
The device advantageously comprises as many U-brackets as annular segments, with each annular segment enclosing one of the U-brackets when the connecting component is in its assembled position.